Insecticidal potential of bioactive compounds extracted from Phyllanthus acidus L. leaf against medically important mosquito species

Mosquitoes are major disease vectors, causing millions of deaths annually. Resistance to chemical insecticides has reduced their effectiveness, prompting the need for safer alternatives, such as plant-derived phytochemicals. This research assessed the effectiveness of solvent extracts derived from mature Phyllanthus acidus leaves on different developmental stages of Culex quinquefasciatus, Culex vishnui, and Aedes albopictus. Six solvent extracts, namely petroleum ether, n-hexane, ethyl acetate, chloroform: methanol (1:1 v/v), acetone, and ethanol, were prepared using leaves. Among them, ethanol leaf extract showed the highest larvicidal, pupicidal, adulticidal, and repellent activities. The ethanol extracts demonstrated significant mosquito mortality, with LC₅₀ values of 21.32, 18.87, and 51.62 ppm for third instar larvae of Cx. quinquefasciatus, Cx. vishnui, and Ae. albopictus, respectively. The pupicidal activity was notably higher in ethanol-based leaf extracts, with an LC₅₀ value of 98.44 ppm with Cx. vishnui being the most susceptible species. In adulticidal and smoke toxicity tests, ethanol leaf extracts showed strong effects, causing 86.74–96.18% knockdown. Effective extracts were further purified using column and thin-layer chromatography. FTIR analysis identified several bioactive functional groups, such as hydroxyl, nitro, alkoxy, amino, and halogen groups. LC–MS analysis confirmed the presence of jatrorrhizine (C₂₀H₂₀NO₄), a potent alkaloid with known biological activity that interferes with mosquito physiology by disrupting neurotransmission, altering enzyme functions, impairing respiration, and compromising the integrity of the midgut. Importantly, bioassays showed no toxicity toward non-target organisms. The data suggest that the ethanol extract of the leaves of P. acidus shows promise as an eco-friendly agent for controlling medically significant vectors.